74« INTERNAL ANATOMY OF INSECTS. 
sal and ventral segments — in the Libellulina by similar 
ventral folds ; and in Cimbex by membranous pieces in 
the first dorsal segment, which De Geer observed was 
elevated and depressed at the will of the animal a . 
Air is as essential to insects in their pupa as in their 
larva or perfect states. Lyonet, however, Musschen- 
broek, Martinet, and some other physiologists, have 
doubted whether quiescent pupae breathed b ; but Reau- 
mur and De Geer seem to have proved that they do c : 
and if thrown into water, the same proof of respiration, 
by the emission and retraction of a bubble of air takes 
place, as in the larvae ; and De Geer found that if one 
be transferred under water from one spiracle to another, 
it will be absorbed by it d . Indeed, unless these pupae 
had breathed, where would have been the necessity for 
the spiracles with which all are furnished? It is remark- 
able, however, that all these spiracles do not seem of 
equal importance in this respect. Reaumur found that 
if the posterior spiracles only were closed with oil, the 
insect suffered no injury; but that if the anterior ones 
were similarly treated, it infallibly died e . The respira- 
tion however of pupae seems more perfect in those that 
have recently assumed that state, than in those that are 
more advanced towards the imago; in which at first, from 
Reaumur's experiments f , it appears that the posterior 
spiracles were stopped ; and in others still older, from 
Musschenbroek's s, even the anterior ones. Those quies- 
cent pupae that during that state remain submerged, re- 
a De Geer ii. 946—. 
b Lesser, L. i. 124. note*. Lyonet Anatom. pref. xii. De Geerii. 
132. c lteaum. i. 399-. De Geer i. 37— . 
11 Ibid. 40. e Reauiu. i. 400. f Ibid. E De Geer ii. 129. 
